Fluorocarbon elastomers are synthetic elastomeric polymers with a high fluorine content. See, for example, W. M. Grootaert et al., "Fluorocarbon Elastomers", Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 8, pp. 990-1005 (4th ed., John Wiley & Sons, 1993). Fluorocarbon elastomers, particularly the copolymers of vinylidene fluoride (VF2) with other ethylenically unsaturated halogenated monomers, such as C.sub.3 F.sub.6 (hexafluoropropylene or HFP), have become the polymers of choice for high temperature applications, such as seals, gaskets, and linings, especially when shaped articles thereof are subject to exposure to aggressive or harsh environments, such as solvents, lubricants, and oxidizing or reducing conditions. See, for example, U.S. Pat. No. 4,912,171 (Grootaert et al.), which discloses a fluoroelastomeric polymer prepared from VF2, tetrafluoroethylene (TFE), and a copolymerizable hydrocarbon olefin.
A major drawback to many applications of shaped articles made of such fluorocarbon elastomers has been their inability to satisfactorily function at low temperatures. Typically, at temperatures only slightly below 0.degree. C., shaped articles made from copolymers of VF2 and HFP become stiff and fail to perform satisfactorily.
Low temperature flexibility of VF2 elastomers may be improved by substituting perfluoro(alkyl vinyl ethers) for the HFP in VF2/HFP/TFE copolymers as discussed in U.S. Pat. No. 5,214,106 (Carlson et al.). However, the resulting polymers cannot be cured by the onium/bisphenol cure system disclosed in U.S. Pat. No. 4,912,171 (Grootaert et al.), without destroying the ether linkage as shown in A. L. Logothetis, Prog. Polym. Sci., 14, 251-296 (1989). Thus, there is a need for low temperature elastomeric materials that can be readily cured using the onium/bisphenol cure system or diamine cure systems.